Gas filling system, and vehicle

ABSTRACT

A vehicle includes: a fuel tank into which gas is filled from a gas station that has a receiver; a transmitter; and a control device connected to the transmitter. The control device changes a transmission cycle of a signal transmitted from the transmitter to the receiver during the gas filling from the gas station into the fuel tank, according to a state quantity regarding an interior of the fuel tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a gas filling system that fills gas from a gas station into, for example, a vehicle-mounted fuel tank, and also relates to a vehicle equipped with such a fuel tank.

2. Description of the Related Art

Known gas stations as mentioned above include a hydrogen station that fills hydrogen gas into a hydrogen tank of a fuel cell vehicle (see, for example, Japanese Patent Application Publication No. 2005-069327 (JP-A-2005-069327)) and Japanese Patent Application Publication No. 2007-321572 (JP-A-2007-321572)). In Japanese Patent Application Publication No. 2005-069327 (JP-A-2005-069327), the vehicle and the hydrogen station are electrically connected via an adaptor, and information about the maximum service pressure of the hydrogen tank of the vehicle is grasped at a hydrogen station side in order to control hydrogen filling so that the maximum service pressure will not be exceeded.

While hydrogen is being filled, it is desirable to monitor the temperature and the pressure in the hydrogen tank which rise in association with the hydrogen filling. In conjunction with this respect, consideration has been given to a construction in which, through the use of a communication equipment, signals regarding the temperature and the like in the fuel tank are sent from the vehicle side and the hydrogen station as need arises, and the hydrogen station automatically stops the hydrogen filling before the allowable temperature (reference value) of the hydrogen tank is exceeded (see, Japanese Patent Application Publication No. 2007-321572 (JP-A-2007-321572)).

By the way, the hydrogen filling sometimes requires a long time, depending on conditions. For example, during the daytime under a blazing sun, the hydrogen tank is exposed to an environment whose temperature is higher than normal temperature. If, in view of this situation, the hydrogen filling is performed at slower filling speed than at normal temperature so that the temperature of the hydrogen tank will not exceed its allowable temperature, the filling time becomes long. If during such a long-time filling, data about, for example, temperature in the hydrogen tank, and the like, is transmitted from the vehicle side to the hydrogen station side as need arises, there is a possibility that the electric power source of the vehicle, which is at rest, may lack power.

SUMMARY OF THE INVENTION

The invention provides a gas filling system and a vehicle that reduce the electric power consumed during the gas filling.

A gas filling system in accordance with a first aspect of the invention includes: a vehicle having a fuel tank, a transmitter, and a control device that is connected to the transmitter; and a gas station having a receiver that receives a signal from the transmitter, wherein the control device changes a transmission cycle of the signal that is transmitted from the transmitter to the receiver during gas filling from the gas station to the fuel tank, according to a state quantity regarding an interior of the fuel tank.

A vehicle in accordance with a second aspect of the invention includes: a fuel tank into which gas is filled from a gas station that has a receiver; a transmitter; and a control device that is connected to the transmitter, and that changes a transmission cycle of a signal transmitted from the transmitter to the receiver during the gas filling from the gas station to the fuel tank, according to a state quantity regarding an interior of the fuel tank.

According to the first and second aspects of the invention, the signal transmission cycle used during the gas filling is not fixed, but is changed according to a state quantity regarding the interior of the fuel tank. Due to this construction, for example, in the case where the interior of the fuel tank has such a state quantity that the filling time will be long, selective use of a long transmission cycle will reduce the electric power needed for the transmission from the transmitter in a single operation of gas filling as a whole. Hence, the electric power consumption during gas filling can be reduced.

In the first and second aspect of the invention, the state quantity regarding the interior of the fuel tank may include temperature and pressure in the fuel tank, and if the temperature in the fuel tank is greater than or equal to a first threshold value and the pressure in the fuel tank is less than or equal to a second threshold value, the control device may make the transmission cycle longer than if the temperature in the fuel tank is less than the first threshold value or if the pressure in the fuel tank is greater than the second threshold value.

According to this construction, in the former case, in which the filling time will be longer than in the latter case, a longer transmission cycle can be used to reduce the electric power consumption during the gas filling. In particular, since the temperature and the pressure in the fuel tank are both compared with their respective threshold values, the state in the fuel tank can be precisely grasped, so that the length of the transmission cycle can be appropriately determined.

It is to be noted herein that the first threshold value and the second threshold value each vary depending on the kinds of gas. In an example case where hydrogen gas is filled, the first threshold value is 60° C., and the second threshold value is 2 MPa.

The vehicle may further include: a temperature sensor that detects the temperature in the fuel tank; a pressure sensor that detects the pressure in the fuel tank, and the temperature in the fuel tank that is compared with the first threshold value may be the temperature that the temperature sensor detects before the gas filling starts, and the pressure in the fuel tank that is compared with the second threshold value may be the pressure that the pressure sensor detects before the gas filling starts.

According to this construction, the length of the signal transmission cycle during gas filling is determined on the basis of the temperature and the pressure in the fuel tank which are grasped prior to the start of gas filling. This makes it possible to use a long signal transmission cycle from the start of gas filling, so that it becomes possible to further reduce the electric power consumption.

The signal transmitted from the transmitter to the receiver during the gas filling may include detection information about the temperature and the pressure in the fuel tank that the temperature sensor and the pressure sensor detect during the gas filling.

According to this construction, it is possible to detect the temperature and the pressure in the fuel tank during the gas filling at the side of the gas station while restraining the electric power consumption needed for the transmission performed by the transmitter.

The gas station may have a station-side control device that is connected to the receiver, and the station-side control device may control the gas filling into the fuel tank based on the detection signal that the receiver receives.

According to this construction, at least one condition in the gas filling suitable to the pressure and the temperature in the fuel tank during the gas filling, for example, at least one of the filling speed and the amount of filling, can be changed.

In the foregoing construction, during the gas filling, if the receiver does not receive the signal from the transmitter during a predetermined cycle, the station-side control device may determine that a transmission error has occurred, and the control device may set the transmission cycle at less than half of the predetermined cycle.

According to this construction, it becomes possible to perform a process in terms of control in which it is determined that there is no abnormality occurring in the transmitter despite actual occurrence of a transmission error if the occurrence of the transmission error is the first occurrence, even in the case where a long transmission cycle is used.

The vehicle may have an electricity storage device that supplies electric power to the temperature sensor, the pressure sensor, the transmitter and the control device.

Since measures are provided to reduce the electric power consumption during the gas filling as mentioned above, the power shortage of the electricity storage device during gas filling can be restrained. This restrains, for example, occurrence of an event that the temperature sensor or the like cannot input information.

The control device may use a first transmission cycle if an elapsed time following start of the gas filling is less than or equal to a third threshold value, and the control device may use a second transmission cycle that is longer than the first transmission cycle if the elapsed time exceeds the third threshold value.

According to this construction, in the case of a long-time gas filling that lasts longer than the third threshold value, the electric power consumption during gas filling can be reduced.

The transmitter and the receiver may be infrared communication instruments.

This construction reduces the electric power consumption during the gas filling for which infrared communication is used.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages, and technical and industrial significance of this invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic diagram of a gas filling system in accordance with an embodiment of the invention;

FIG. 2 is a construction diagram of a gas filling system in accordance with the embodiment of the invention;

FIG. 3 is a flowchart showing an operation procedure that a gas filling system in accordance with the embodiment of the invention performs before starting filling gas;

FIG. 4 is a flowchart showing an operation procedure of determining a transmission cycle in accordance with a first modification of the embodiment of the invention; and

FIG. 5 is a flowchart showing an operation procedure of determining a transmission cycle in accordance with a second modification of the embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described hereinafter with reference to the drawing. The following description will be made in conjunction with an example of a gas filling system in which hydrogen gas is filled from a hydrogen station into a fuel tank of a fuel cell vehicle equipped with a fuel cell system. Incidentally, the fuel cell system includes a fuel cell that generates electricity by electrochemical reaction between a fuel gas (e.g., hydrogen gas) and an oxidizing gas (e.g., air). Besides, the filling of hydrogen gas is one manner of supplying hydrogen gas from the hydrogen station into the fuel tank.

As shown in FIG. 1, a gas filling system 1 includes, for example, a hydrogen station 2 as a gas station, and a vehicle 3 that is supplied with hydrogen gas from the hydrogen station 2.

As shown in FIG. 2, the vehicle 3 includes a fuel tank 30, a receptacle 32, a pressure sensor 36, a temperature sensor 38, a display device 42, a communication instrument 44, and a control device 46. The fuel tank 30 is a fuel gas supply source for the fuel cell, and, for example, is a high-pressure tank that is capable of storing hydrogen gas at 35 MPa or 70 MPa. In the case where a plurality of fuel tanks 30 are mounted in the vehicle 3, the fuel tanks 30 are connected in parallel to the fuel cell. The hydrogen gas in the fuel tank 30 is supplied to the fuel cell 50 through a supply channel 52. On the other hand, the supply of hydrogen gas to the fuel tank 30 is carried out by the hydrogen station 2 releasing hydrogen gas into a filling channel 34 through a receptacle 32. The filling channel 34 is made up of a gas piping provided outside the fuel tank 30, and a channel portion that is provided in a valve assembly (not shown) that is attached to an opening portion of the fuel tank 30. Besides, the filling channel 34 is provided with a check valve 35 for restraining reverse flow of the hydrogen gas.

The pressure sensor 36 detects the pressure of the hydrogen gas released from the hydrogen station 2, and is provided in the filling channel 34. For example, the pressure sensor 36 is provided in the foregoing gas piping that is provided at a downstream side of the check valve 35 and that is immediately upstream of the fuel tank 30, and detects a pressure that substantially reflects the pressure of the hydrogen gas within the fuel tank 30 (hereinafter, referred to as “tank pressure”). The temperature sensor 38 is provided in a channel portion in the valve assembly, and is disposed within the fuel tank 30. The temperature sensor 38 detects a temperature that reflects the temperature of hydrogen gas within the fuel tank 30 (hereinafter, referred to as “tank temperature”). Incidentally, in other embodiments, the pressure sensor 36 may also be disposed within the fuel tank 30. Besides, the position in the fuel tank 30 at which the temperature sensor 38 is disposed is not particularly limited as long as the position allows the tank temperature to be substantially detected. It is preferable that the temperature sensor 38 be provided near a blowout opening that leads hydrogen gas into the fuel tank 30.

The display device 42 is able to be used, for example, as a portion of a car navigation system, and displays various kinds of information in its display screen. The communication instrument 44 is provided for communicating with the hydrogen station 2, and, for example, as a communication interface for wireless communication such as an infrared communication and the like. The communication instrument 44 is built in the receptacle 32 or is fixed within a lidded box of the vehicle 3 so as to be capable of communication when a filling nozzle 12 of the hydrogen station 2 is connected to the receptacle 32.

The control device 46 is constructed as a microcomputer that has therein a CPU, a ROM and a RAM. The control device 46 controls the vehicle 3. The CPU executes desired computations according to control programs so as to perform various processes and controls, such as changing the transmission cycle of the communication instrument 44. The ROM stores control programs and control data that are processed by the CPU. The RAM is used mainly as various workspaces for control processes. The control device 46 is connected to the pressure sensor 36, the temperature sensor 38, a display device 42, a communication instrument 44, etc., and sends, for example, information detected by the pressure sensor 36 and the temperature sensor 38, to the hydrogen station 2 by using the communication instrument 44.

A high-voltage DC/DC converter 54 that controls the output voltage of the fuel cell 50 is connected to the fuel cell 50. Various high-voltage accessories 56 that are used for the operation of the fuel cell 50 are electrically connected between the fuel cell 50 and the high-voltage DC/DC converter 54. The high-voltage accessories 56 are accessories that need high voltage (e.g., a voltage above 12 V), for example, an air compressor that pressure-feeds an oxidizing gas to the fuel cell 50, a hydrogen pump that supplies an hydrogen off-gas to the fuel cell 50 in a circulating manner. The electricity storage device 58 is a chargeable-dischargeable secondary cell that functions as a high-voltage electricity storage device. The electricity storage device 58 is connected to, for example, a traction motor of the vehicle 3 via the high-voltage DC/DC converter 54, in parallel with the fuel cell 50.

A low-voltage DC/DC converter 60 is electrically connected between the high-voltage DC/DC converter 54 and the electricity storage device 58. The low-voltage DC/DC converter 60 lowers the voltage of a portion of the direct-current power of a high-voltage circuit side, and supplies the lowered-voltage power to a low-voltage circuit side. The lowered-voltage direct-current power is partially used to charge the low-voltage battery 62, and is partially used as power to drive low-voltage accessories 64. The low-voltage battery 62 functions as an electricity storage device of low voltage (e.g., 12 V), and is a secondary cell that is represented by, for example, a nickel metal hydride cell, a lithium ion cell. The low-voltage accessories 64 are various appliances that are driven at low voltage, and are different from the high-voltage accessories 56. What are regarded as the low-voltage accessories 64 are, for example, the pressure sensor 36, the temperature sensor 38, the display device 42, the communication instrument 44, etc. The low-voltage accessories 64 and the control device 46 are also driven when supplied with electric power from the low-voltage battery 62 as a power supply source. For example, while the vehicle 3 is in an ignition-off state (hereinafter, referred to as “IGOFF”), the fuel cell 50 does not generate electricity, and therefore the power for the low-voltage accessories 64 and the control device 46 is supplied from the low-voltage battery 62.

The hydrogen station 2 includes a control device 5 that controls various appliances and the like that are provided at the hydrogen station 2, a communication instrument 6 for communicating with the vehicle 3, a display device 7 that displays various kinds of information in its display screen, and an outside air temperature sensor 8 that detects the outside air temperature at the location where the hydrogen station 2 is installed. The communication instrument 6 is of a type that is pursuant with the communication instrument 44 of the vehicle 3, and sends and receives various kinds of information to and from the communication instrument 44. The display device 7 displays information such as the filling speed (filling flow rate) and the filling amount during the filling operation, and the like. Besides, the display screen of the display device 7 is equipped with an operation panel on which an operating person or a user (hereinafter, collectively referred to as “user”) is allowed to input a desired filling condition. That is, the user is allowed to designate a complete filling of the tank (complete filling), a desired filling amount, a desired amount of money to be paid for a single operation of filling, etc., as desired filling conditions, via the operation panel of the display device 7. Incidentally, in other embodiments, it is also permissible to adopt a construction that is able to receive filling conditions input from a user by using a device different from the display device 7.

Besides, the hydrogen station 2 has a cluster of tanks (a gas supply source) 11 that stores hydrogen gas, a filling nozzle 12 that releases hydrogen gas toward the fuel tank 30 mounted in the vehicle 3, and a gas channel 13 that connects the cluster of tanks 11 and the filling nozzle 12. The filling nozzle 12 is also called filling coupling, and is connected to the receptacle 32 of the vehicle 3 when hydrogen gas is filled into the vehicle 3. The filling nozzle 12 and the receptacle 32 form a connecting unit that connects the hydrogen station 2 and the fuel tank 32. Besides, the filling nozzle 12 is provided with a pressure sensor 9 and a temperature sensor 10 that detect the pressure and the temperature of hydrogen gas that the hydrogen station 2 supplies to the fuel tank 30. Due to the provision of these sensors 9 and 10 on the filling nozzle 12, the actual pressure and the actual temperature of the hydrogen that is actually supplied from the hydrogen station 2 to the fuel tank 30 can be acquired by a simple construction. Besides, it is preferable that the temperature sensor 10 be provided at a distal end of the filling nozzle 12 (a fuel tank 30-side portion of the filling nozzle 12).

The gas channel 13 is provided with a compressor 14, a pressure accumulator 15, a pre-cooler 16, a flow control valve 17, a flow meter 18 and a dispenser 19. The compressor 14 compresses hydrogen gas from the cluster of tanks 11, and discharges it. The pressure accumulator 15 stores hydrogen gas whose pressure has been raised to a predetermined pressure by the compressor 14. The pre-cooler 16 cools the hydrogen gas from the pressure accumulator 15 whose temperature is approximately equal to room temperature to a predetermined low temperature (e.g., −20° C. or −40° C.). The flow control valve 17 is an electrically driven valve, and adjusts the amount of flow of hydrogen gas from the pressure accumulator 15 in accordance with a command from the control device 5. Due to this, the filling flow rate (filling speed) of hydrogen gas to the fuel tank 30 is controlled. This controlled filling flow rate is measured by the flow meter 18. In response to a result of the measurement, the control device 5 performs a feedback control of the flow control valve 17 so as to achieve a desired filling flow rate. Incidentally, it is also possible to use a flow rate control device other than the flow control valve 17. The dispenser 19 is sends out hydrogen gas to the filling nozzle 12. For example, if a trigger lever of the filling nozzle 12 is pulled, the dispenser 19 is actuated to become able to discharge hydrogen gas from the filling nozzle 12 toward the fuel tank 30. Incidentally, although not shown in the drawings, a shutoff valve that opens the gas channel 13 during the filling operation is provided in the pressure accumulator 15 or at a downstream side of the pressure accumulator 15.

The control device 5 is constructed as a microcomputer that has therein a CPU, a ROM and a RAM. The CPU executes desired computations according to control programs so as to perform various processes and controls. The ROM stores control programs and control data that are processed by the CPU. The RAM is used mainly as various workspaces for control processes. The control device 5 is electrically connected to the communication instrument 6, the display device 7, the outside air temperature sensor 8, the pressure sensor 9, the temperature sensor 10, the flow control valve 17, the flow meter 18, the pressure accumulator 15, etc., which are connected by a control line shown by a dashed one-dotted line in FIG. 2. For example, the control device 5 recognizes the pressure and the temperature that the pressure sensor 36 and the temperature sensor 38 detect, as the pressure and the temperature in the fuel tank 30 (i.e., the tank pressure and the tank temperature) of the vehicle 3, and accordingly controls the filling of hydrogen gas. Specifically, the control device 5 controls the degree of opening of the flow control valve 17 on the basis of the information regarding the tank pressure and the tank temperature of the vehicle 3 side which the control device 5 receives from the communication instrument 6. Besides, the control device 5 sends information that is obtainable at the hydrogen station 2 to the communication instrument 44 of the vehicle 3, by using the communication instrument 6.

Thus, the communication instruments 6 and 44 function as receivers and transmitters that receive and transmit signals that include various kinds of information from and to each other. As the communication instruments 6 and 44, it is possible to use infrared communication instruments that each include a transmission element and a reception element. The transmission element and the reception element of each communication instrument may be constructed of, for example, an infrared light-emitting diode and a photodiode, respectively.

In the gas filling system 1 described above, when hydrogen gas is to be filled into the vehicle 3, the filling nozzle 12 is firstly connected to the receptacle 32, and then the dispenser 19 is actuated while the connection therebetween is maintained. Then, hydrogen gas is released from the filling nozzle 12 toward the fuel tank 30, and is therefore filled into the fuel tank 30. In the gas filling system 1 of this embodiment, before the filling is started, the state quantity regarding an interior of the fuel tank 30 is grasped. If the state quantity satisfies a predetermined condition, the cycle of the transmission from the vehicle 3 to the communication instrument 44 of the hydrogen station 2 is elongated (i.e., the next transmission timing is delayed). In this manner, the electric power consumption during the gas filling is minimized.

Next, an operation procedure of determining the transmission cycle of the communication instrument 44 in the gas filling system 1 will be described with reference to FIG. 3. The procedure shown in FIG. 3 is executed before the filling of hydrogen gas from the hydrogen station 2 into the fuel tank 30 is started.

Firstly, the electric power source of the control device 46 of the vehicle 3 is turned on (step S1). This is carried out by supplying electric power from the low-voltage battery 62 to the control device 46. Examples of the trigger of turning on the electric power source of the control device 46 includes detecting that the operation of connecting the filling nozzle 12 and the receptacle 32 has been performed, by means of a sensor (not shown). It is also permissible to detect that a fuel cover of a lidded box of the vehicle 3 has been opened, by means of a sensor, through the use of a method different from the foregoing method. When the electric power source of the control device 46 is turned on, the pressure sensor 36, the temperature sensor 38 and the communication instrument 44 are activated. The activation of these devices and the like is carried out by the supply of electric power from the low-voltage battery 62.

Then, after the activation of the pressure sensor 36 and the temperature sensor 38 is completed, a tank pressure P₁ and a tank temperature T₁ (hereinafter, sometimes referred to as “initial tank pressure” and “initial tank temperature”, respectively) are input as state quantities of the fuel tank 30 occurring before the filling starts. Information about the tank pressure P₁ and the tank temperature T₁ that are input is temporarily stored into, for example, the RAM of the control device 46. On the other hand, simultaneously with or prior or subsequently to the completion of the activation of the pressure sensor 36 and the temperature sensor 38, the activation of the communication instrument 44 is completed. At this time, if the operation of connecting the filling nozzle 12 and the receptacle 32 has been completed, a state in which wireless communication is possible between the hydrogen station 2 and the vehicle 3 is established.

Next, in step S2, it is determined whether or not the tank temperature T₁ is greater than or equal to a threshold value T_(th). This determination is carried out by the control device 46. The threshold value T_(th) is determined beforehand, by factoring in the filling time, and is stored beforehand in the ROM of the control device 46.

Concretely, through an evaluation test or a simulation performed beforehand, it is possible to grasp the approximate lengths of the filling time corresponding to various tank temperatures and various tank pressures. For example, through a prior evaluation, it has been ascertained that when the tank temperature of a fuel tank is greater than or equal to 60° C. and the tank pressure thereof is less than or equal to 2 MPa, the filling time required is greater than or equal to 40 minutes. The filling time tends to be longer the higher the tank temperature. Therefore, when the tank temperature is about normal temperature, a long filling time that is greater than or equal to 40 minutes is not required. In view of what has been described above, the threshold value T_(th) in this embodiment is set at a tank temperature that has been ascertained to require a long filling time (e.g., 40 minutes or more) through a prior evaluation or the like. An example of the threshold value T_(th) is 60° C.

However, the threshold value T_(th) varies depending on the characteristics (heat dissipation characteristic) of the fuel tank 30 and also on the reference temperature (allowable temperature) of the fuel tank 30, the cooling capability of the pre-cooler 16, etc. That is, differences in these factors vary the filling time. For example, the heat dissipation characteristic of the fuel tank 30 is better in the case where aluminum is used as a liner of the fuel tank 30 than in the case where a resin (polyethylene or the like) is used as the liner. Therefore, in the former case, it is possible to increase the threshold value T_(th). Besides, the rise of the tank temperature caused by the filling can be made less the lower the temperature of hydrogen gas that can be achieved by the pre-cooler 16.

Therefore, it is also possible to make the threshold value T_(th) larger the higher the cooling capability of the pre-cooler 16. Therefore, while the threshold value T_(th) in step S2 can be a fixed value (60° C. as in the foregoing example), the threshold value Tth can also be varied on the basis of a characteristic of the fuel tank 30 or the like. Incidentally, it should be apparent that in the case where the gas to be filled in is a gas that is different in kind from hydrogen gas, the threshold value T_(th) used is also different from that used in the case where the gas to be filled in is hydrogen gas.

If it is determined in step S2 that the tank temperature T₁ is less than the threshold value T_(th) (NO in step S2), it is considered that the filling time required is not very long. Therefore, the control device 46 determines that a transmission cycle T_(A) is to be used, without taking the tank pressure P₁ into account (step S3). On the other hand, if the tank temperature T₁ is higher than or equal to the threshold value T_(th) (YES in step S2), it is considered that a long filling time will be required. Therefore, the control device 46 compares the tank pressure P₁ with the threshold value P_(th) (step S4).

The threshold value P_(th), similar to the threshold value T_(th), is determined beforehand by taking the filling time into account, and is stored beforehand in the ROM of the control device 46. In this case, the filling time tends to be long the lower the tank pressure. The threshold value P_(th) in this embodiment is set at a tank pressure that has been ascertained to require a long filling time (e.g., 40 minutes or more) through a prior evaluation or the like. An example of the threshold value P_(th) is 2 MPa. It is to be noted herein that the threshold value P_(th), similar to the threshold value T_(th), may be a fixed value, or may also be varied on the basis of characteristics (heat dissipation characteristic) of the fuel tank 30, the reference temperature (allowable temperature) of the fuel tank 30, or the cooling capability of the pre-cooler 16, etc.

If in step S4 it is determined that the tank pressure P₁ is greater than the threshold value P_(th) (NO in step S4), it is considered that the filling time will not be long, and therefore it is determined to use a signal transmission cycle T_(A) (step S3). On the other hand, if the tank pressure P₁ is less than or equal to the threshold value P_(th) (YES in step S4), it is considered that the filling time will be long. Therefore, the control device 46 determines to use a signal transmission cycle T_(B) that is longer than the transmission cycle T_(A) (step S5).

The transmission cycles T_(A) and T_(B) will be described. The term “transmission cycles T_(A) and T_(B)” refers to a cycle period of a signal that the communication instrument 44 transmits to the communication instrument 6. That is, the time duration from when the communication instrument 44 transmits a signal to the communication instrument 6 to when the communication instrument 44 transmits the next signal to the communication instrument 6 is the transmission cycle. The transmission cycles T_(A) and T_(B) are used for the communication between the communication instrument 44 and the communication instrument 6 during the filling, and are stored beforehand in a storage portion such as the ROM of the control device 46 or the like. In an example, the transmission cycle T_(A) is 100 ms, and the transmission cycle T_(B), which is longer than the transmission cycle T_(A), is 200 ms, 300 ms or 400 ms. However, if there is a standard of the maximum length of the transmission cycle during the filling, the transmission cycles T_(A) and T_(B) are set within a range of the cycle that satisfies the standard maximum length and that does not affect the filling.

It is preferable to determine whether or not a transmission error of the communication instrument 44 has occurred. As an index for the determination, it is advisable to use the presence/absence of reception of a signal from the communication instrument 6 during a fixed period. For example, if during a fixed period (predetermined cycle) of 500 ms, the communication instrument 6 does not receive a signal from the communication instrument 44, it can be determined that a transmission error of the communication instrument 44 has occurred. This determination can be performed by the control device 5 during the filling.

Therefore, in the case where the control device 5 has a reference for determining whether a transmission error of the communication instrument 44 has occurred, it is preferable to set the transmission cycles T_(A) and T_(B) at less than half of the predetermined cycle period that is used according to the foregoing reference. Concretely, in the foregoing example, in the case where the predetermined cycle period is 500 ms, it is preferable that the transmission cycle T_(B) be set at 200 ms, which is less than 250 ms. This setting makes it possible for the control device 5 to perform a process in terms of control in which a transmission error, if occurring for the first time, is assumed to be no occurrence of abnormality in the communication instrument 44. This setting is particularly useful in the case where the reliability of communication is low. Incidentally, in the case where the reliability of communication is high, the transmission cycle T_(B) may be set at a half or more of the predetermined cycle period.

After the transmission cycle T_(A) or T_(B) is determined (step S3 or S5), the communication during the filling is performed at the determined transmission cycle. More specifically, after the determination of the transmission cycle, information about the initial tank pressure and the initial tank temperature is transferred to the control device 5 of the hydrogen station 2. Next, the control device 5 looks up the initial tank pressure and the initial tank temperature that are received in a filling speed map, and starts the filling so as to achieve a filling speed that corresponds to the initial tank pressure and temperature.

During the filling, the tank pressure and the tank temperature are input as needed, and a signal that contains information about the tank pressure and the tank temperature that are input is transmitted from the communication instrument 44 to the communication instrument 6 at the determined transmission cycle T_(A) or T_(B). Owing to this, the control device 5 monitors the tank pressure and the tank temperature during the filling. Then, the control device 5 looks up the tank pressure and the tank temperature that the control device 5 monitors in the filling speed map, and controls the degree of opening of the flow control valve 17 so as to change the filling speed according to need. Incidentally, during the filling, the vehicle 3 is in an IGOFF state, so that the electric power for the communication instrument 44 is supplied by the low-voltage battery 62.

As the filling operation completes a filling that satisfies a desired filling condition that the user has designated, the supply of hydrogen gas to the fuel tank 30 is stopped, and the filling ends. After that, the filling nozzle 12 is detached from the receptacle 32, and the power source of the pressure sensor 36, the temperature sensor 38 and the communication instrument 44 is turned off, that is, the supply of electric power thereto from the low-voltage battery 62 ends. Then, the electric power source of the control device 46 is also turned off.

Operation and effects of the foregoing embodiment will be described. During the communication-based filling of the fuel tank 30, the electric power source used for the communication instrument 44 and the like in the vehicle 3 is the low-voltage battery 62. Therefore, if the transmission cycle T_(A), which is relatively short, is used during the filling whose filling time is long, there arises possibility of power shortage of the low-voltage battery 62.

In this embodiment, in the case where it is determined from the initial tank temperature and the initial tank pressure that the filling time will be long, the transmission cycle T_(B), which is relatively long, is used during the filling. Therefore, during the entire single operation of filling, the electric power needed for the communication via the communication instrument 44 decreases, so that the electric power consumption during the filling can be reduced. Therefore, it is possible to restrain the low-voltage battery 62 from entering a so-called dead state.

Incidentally, although in the foregoing embodiment, a transmission cycle is determined before the filling is started, it is also possible to perform steps S2 to S4 in FIG. 3 after the filling is started. In this case, the length of the transmission cycle is determined from the state quantity (tank temperature, tank pressure) regarding the interior of the fuel tank 30 after the filling is started, and is then used.

MODIFICATIONS

Modifications of the foregoing embodiment will be described. The following modifications are applicable to each other.

First Modification

A first modification shown in FIG. 4 is different from the foregoing embodiment mainly in that the transmission cycles T_(A) and T_(B) are determined on the basis of the elapsed time in the filling.

Firstly, after the same process as in step S1 in FIG. 3 is performed (step S11), a filling speed corresponding to the initial tank pressure and the initial tank temperature is selected from a filling speed map, and the filling of the fuel tank 30 is accordingly started (step S12). Next, the elapsed time following the start of the filling (hereinafter, referred to as “elapsed filling time”) is measured by a timer (not shown), and it is checked whether or not the elapsed filling time is greater than a predetermined threshold value (third threshold value) (step S13). This checking can be performed by the control device 46 of the vehicle 3. The predetermined threshold value can be arbitrarily set; for example, it can be set at 20 minutes or 40 minutes.

If in step S13 it is checked that the elapsed filling time is less than or equal to the predetermined threshold value (NO in step S13), it is determined to use the transmission cycle T_(A), and the filling is accordingly continued (step S14). On the other hand, if the elapsed filling time is longer than the predetermined threshold value (YES in step S13), it is determined to use the transmission cycle T_(B), which is longer than the transmission cycle T_(A), and the filling is accordingly continued (step S15). Therefore, according to the first modification, in the case of a long-time filling whose filling time exceeds the predetermined threshold value, the electric power consumption during the filling can be reduced.

Incidentally, in step S13, it is also permissible to compare an activation time of the communication instrument 44 with a threshold value (e.g., 20 minutes or 40 minutes). In this case, when the filling is started in step S12, the hydrogen station 2 has not grasped the initial tank pressure nor the initial tank temperature yet, and therefore the filling is started at a filling speed that is set by taking safety into account. For example, the filling is started by using as an initial tank pressure the pressure hydrogen gas supplied from the hydrogen station 2 (e.g., detected at the nozzle 12) or a higher pressure, and using as an initial tank temperature the outside air temperature (a value detected by the outside air temperature sensor 8) or a temperature below the detected value.

The first modification can be performed independently of the operation procedure shown in FIG. 3, or can also be incorporated into the procedure shown in FIG. 3. In the latter case, the process of steps S12 to S15 shown in FIG. 15 is incorporated after the process of steps S3 and S5 shown in FIG. 3.

Second Modification

A second modification shown in FIG. 5 is different from the foregoing embodiment mainly in that the transmission cycles T_(A) and T_(B) are determined on the basis of the voltage of the low-voltage battery 62, which is a battery for accessories.

Firstly, in step S21, the same process as in step S1 in FIG. 3 is performed. Next, in step S22, the voltage of the low-voltage battery 62 (the state of charge thereof) is detected by an SOC sensor (not shown), and it is checked whether or not the detected voltage of the low-voltage battery 62 is less than or equal to a predetermined threshold value (step S22). This checking can be performed by the vehicle 3-side control device 46. The predetermined threshold value for use for comparison in step S22 can be arbitrarily set; for example, it can be set at a voltage that corresponds to 20% or 30% of the full voltage (full state or charge).

If in step S22 it is checked that the voltage of the low-voltage battery 62 is greater than the predetermined threshold value (NO in step S22), it is determined that the dead battery will not occur during the filling, and it is determined to use the transmission cycle T_(A) (step S23). On the other hand, if the voltage of the low-voltage battery 62 is less than or equal to the predetermined threshold value (YES in step S22), it is determined that the dead battery will occur during the filling, and it is determined to use the transmission cycle T_(B), which is longer than the transmission cycle T_(A). Therefore, according to the second modification, the electric power consumption during the filling can be reduced.

The second modification can be performed independently of the procedure shown in FIG. 3, and can also be incorporated into the procedure shown in FIG. 3. In the latter case, the procedure shown in FIG. 3 is performed before the filling is started, and during the filling, the process of steps S22 to S24 shown in FIG. 5 is performed by monitoring the voltage of the low-voltage battery 62.

Third Modification

It is also possible to adopt a construction in which the functions of the vehicle 3-side control device 46 is to two control devices, and in which both control devices receive electric power from the low-voltage battery 62. For example, in a construction in which a fuel-cell control device for use for the electricity generation control of the fuel cell 50 and a filling control device for use for the control of communication-based filling are used, it suffices that the filling control device is equipped with functions needed for the foregoing communication-based filling which are performed by the control device 46 in the foregoing embodiment (functions that are needed in order to execute the procedures shown in FIGS. 3 to 5). In this construction, the process of “turning on the power source of a vehicle-side control device” which is shown in steps S1, S11 and S21 in FIGS. 3 to 5 is performed only for the filling control device, and does not need to be performed for the fuel-cell control device.

The gas filling system and the vehicle of the invention can be applied not only to hydrogen gas, but also to other fuel gases such as natural gas and the like. Besides, the invention is applicable not only to wheeled vehicles but also to other mobile units equipped with fuel tanks as an object of the filling of a fuel gas from outside, such as aircrafts, ships and boats, robots, etc. 

1. A gas filling system comprising: a vehicle having a fuel tank, a transmitter, and a vehicle-side control device that is connected to the transmitter; and a gas station having a receiver that receives a signal from the transmitter, wherein the vehicle-side control device changes a transmission cycle of the signal that is transmitted from the transmitter to the receiver during gas filling from the gas station to the fuel tank that is a time duration from when the transmitter transmits a signal to the receiver to when the transmitter transmits the next signal to the receiver, according to a state quantity regarding an interior of the fuel tank.
 2. The gas filling system according to claim 1, wherein the state quantity regarding the interior of the fuel tank includes temperature and pressure in the fuel tank, and if the temperature in the fuel tank is greater than or equal to a first threshold value and the pressure in the fuel tank is less than or equal to a second threshold value, the vehicle-side control device makes the transmission cycle longer than if the temperature in the fuel tank is less than the first threshold value or if the pressure in the fuel tank is greater than the second threshold value.
 3. The gas filling system according to claim 2, wherein the vehicle has a temperature sensor that detects the temperature in the fuel tank and a pressure sensor that detects the pressure in the fuel tank, and the temperature in the fuel tank that is compared with the first threshold value is the temperature that the temperature sensor detects before the gas filling starts, and the pressure in the fuel tank that is compared with the second threshold value is the pressure that the pressure sensor detects before the gas filling starts.
 4. The gas filling system according to claim 3, wherein the signal transmitted from the transmitter to the receiver during the gas filling includes detection information about the temperature and the pressure in the fuel tank that the temperature sensor and the pressure sensor detect during the gas filling.
 5. The gas filling system according to claim 4, wherein the gas station has a station-side control device that is connected to the receiver, and the station-side control device controls the gas filling into the fuel tank based on the detection signal that the receiver receives.
 6. The gas filling system according to claim 2, wherein the gas station has a station-side control device that is connected to the receiver, and, during the gas filling, if the receiver does not receive the signal from the transmitter during a predetermined cycle, the station-side control device determines that a transmission error has occurred, and the vehicle-side control device sets the transmission cycle at less than half of the predetermined cycle.
 7. The gas filling system according to claim 3, wherein the vehicle has an electricity storage device that supplies electric power to the temperature sensor, the pressure sensor, the transmitter and the vehicle-side control device.
 8. The gas filling system according to claim 2, wherein the vehicle-side control device uses a first transmission cycle as the transmission cycle if an elapsed time following start of the gas filling is less than or equal to a third threshold value, and the vehicle-side control device uses a second transmission cycle that is longer than the first transmission cycle as the transmission cycle if the elapsed time exceeds the third threshold value.
 9. The gas filling system according to claim 2, wherein the transmitter and the receiver are infrared communication instruments.
 10. (canceled)
 11. (canceled)
 12. (canceled)
 13. (canceled)
 14. (canceled) 